Method of preparing a poly(arylene ether), and a poly(arylene ether) prepared thereby

ABSTRACT

A method of preparing a poly(arylene ether) includes oxidatively polymerizing a monohydric phenol in solution, concentrating the solution by removing a portion of the solvent to form a concentrated solution having a cloud point, T cloud , adjusting the temperature of the concentrated solution to at least about (T cloud   −10 ° C.), and combining the concentrated solution with an anti-solvent to precipitate the poly (arylene ether). The method reduces the formation of undesirably fine particles in the product poly(arylene ether).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.09/681895, filed Jun. 21, 2001, now U.S. Pat. No. 6,407,200.

BACKGROUND OF THE INVENTION

Poly(arylene ether) resins are well known and widely used thermoplasticsvalued for properties including heat resistance, stiffness, and highimpact strength. Various methods of preparing poly(arylene ether)homopolymers and copolymers are known, and these materials are oftenisolated and handled as powders.

U.S. Pat. No. 3,306,875 to Hay generally describes oxidation of phenolsto polyphenylene ethers and diphenoquinones. Poly(arylene ether)sprepared include homopolymers of 2,6-dimethylphenol and a copolymer of2,6-dimethylphenol and 2,6-diethylphenol. Poly(arylene ether)s weretypically isolated by combining the polymerization reaction mixture withan anti-solvent, such as methanol, and filtering the resultingprecipitate.

U.S. Pat. No. 4,011,200 to Yonemitsu et al. generally describescopolymers comprising 50-98 mole percent of 2,6-dimethylphenol monomerunits and 50-2 mole percent 2,3,6-trimethylphenol monomer units. Productpoly(arylene ether)s were typically isolated by precipitation andfiltration.

U.S. Pat. No. 4,603,1 94 to Mendiratta et al. generally describes amethod of isolating polymer resins, including poly(arylene ether)s, fromorganic solvents. The method comprises volatilizing the organic solventin the presence of an aqueous slurry of solid polymer particles of aparticular size that provides agglomeration sites for the polymer resinwithin the solution.

U.S. Pat. No. 4,634,761 to Mendiratta et al. generally describes acontinuous process for isolating polymer resins, including poly(aryleneether)s, from organic solvents. The process comprises volatilizing theorganic solvents in an aqueous solution to form polymer granules, andcontrolling the size of the granules by interrupting the feed of theorganic solvent solution.

U.S. Pat. No. 4,906,700 to Banevicius generally describes a process forreduction of odoriferous poly(arylene ether) by-products, such as2,3,6-trimethylanisole, by continuously distilling and recycling thearomatic hydrocarbon solvent used in the poly(arylene ether)polymerization. The poly(arylene ether) preparation method describedincludes a pre-concentration step.

U.S. Pat. No. 6,211,327 B1 to Braat et al. generally describes a processfor producing poly(arylene ether) resins having intrinsic viscosities ofabout 0.08-0.16 deciliters/gram (dL/g) in chloroform at 25° C. Thepoly(arylene ether)s were directly isolated by solvent devolatilization.

European Patent Application No. 153,074 A2 to Kawaki et al. generallydescribes a process for producing a poly(arylene ether) employing acatalyst composed of a cuprous salt and a primary or secondary amine ina mixed solvent consisting of 1 part by weight of a good solvent for theresulting poly(arylene ether) and 0.9 to 1.1 part by weight of a poorsolvent for the resulting poly(arylene ether). The poly(arylene ether)is described as precipitating during the polymerization, and it isisolated by filtration and washing.

European Patent Application 627,466 A2 to Campbell et al. generallydescribes immiscible polymer blends comprising poly(arylene ether)shaving high glass transition temperatures. Example 1 describes thepreparation of a poly(arylene ether) copolymer of 2,6-dimethylphenol and2,3,6-trimethylphenol; the copolymer was isolated by reverseprecipitation with acetone and filtration.

Although some of the above methods enable high yields andproductivities, the poly(arylene ether) powders they produce may includeundesirably high proportions of fines, which are herein defined as solidparticles having a particle size less than about 38 micrometers. It isdesirable to reduce fines, in that their presence may be associated withlosses of the poly(arylene ether) during filtration and drying stages.Other methods may allow the isolation of powders having low content offines, but they are not readily and economically adaptable to alarge-scale manufacturing facility. There remains a need for aneconomical poly(arylene ether) preparation method that producespoly(arylene ether) powders having a reduced content of fines.

SUMMARY OF THE INVENTION

The above-described and other drawbacks and disadvantages of the priorart are alleviated by a method of preparing a poly(arylene ether),comprising: oxidatively coupling a monohydric phenol using anoxygen-containing gas in the presence of a solvent and a complex metalcatalyst to produce a poly(arylene ether) resin; removing a portion ofthe solvent to produce a concentrated solution having a cloud point,T_(cloud); and combining the concentrated solution with an anti-solventto precipitate the poly(arylene ether), wherein the concentratedsolution has a temperature of at least about (T_(cloud)−10° C.)immediately before it is combined with the anti-solvent.

In another embodiment, a method of preparing a poly(arylene ether)comprises: oxidatively coupling 2,6-dimethylphenol and2,3,6-trimethylphenol using an oxygen-containing gas in the presence oftoluene and a complex copper catalyst to produce a poly(arylene ether)copolymer resin; removing a portion of the solvent to produce aconcentrated solution having a cloud point, T_(cloud); and combining theconcentrated solution with an anti-solvent to precipitate thepoly(arylene ether); wherein the concentrated solution has atemperature, T, immediately before it is combined with the anti-solvent;and wherein T satisfies the inequality$T > \left( {\frac{\varphi_{s} - \left( {{0.296 \times {IV}} + {1.27 \times {TMP}} - 35.7} \right)}{1.97\left( {1 - {0.00795 \times {IV}} - {0.0249 \times {TMP}}} \right)} - 10} \right)$

where ø_(S) is the polymer concentration (expressed in weight percent),T_(cloud) is the cloud point of the system (expressed in ° C), IV is theintrinsic viscosity of the copolymer in chloroform at 25° C. (expressedin mL/g), and TMP is the 2,3,6-trimethylphenol content of the copolymer(expressed in weight %).

Other embodiments, including poly(arylene ether) resins preparedaccording to the methods, are described below.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is bar chart showing particle size distribution of a poly(aryleneether) as a function of pre-concentration temperature and high-shearprecipitator rotation rate.

DETAILED DESCRIPTION

One embodiment is a method of preparing a poly(arylene ether),comprising: oxidatively coupling a monohydric phenol using anoxygen-containing gas in the presence of a solvent and a complex metalcatalyst to produce a poly(arylene ether) resin; removing a portion ofthe solvent to produce a concentrated solution having a cloud point,T_(cloud); and combining the concentrated solution with an anti-solventto precipitate the poly(arylene ether), wherein the concentratedsolution has a temperature of at least about (T_(cloud)−10° C.)immediately before it is combined with the anti-solvent.

There is no particular limitation on the monohydric phenol used in thepoly (arylene ether) synthesis. Suitable monohydric phenols includethose having the formula:

wherein each Q¹ is independently halogen, C₁-C₇ primary or secondaryalkyl, phenyl, C₁-C₇ haloalkyl, C₁-C₇ aminoalkyl, C₁-C₇ hydrocarbonoxy,C₂-C₇ halohydrocarbonoxy wherein at least two carbon atoms separate thehalogen and oxygen atoms, or the like; and each Q² is independentlyhydrogen, halogen, C₁-C₇ primary or secondary alkyl, phenyl, C₁-C₇haloalkyl, C₁-C₇ hydrocarbonoxy, C₂-C₇ halohydrocarbonoxy wherein atleast two carbon atoms separate the halogen and oxygen atoms, or thelike. Preferably, each Q¹ is alkyl or phenyl, especially C₁₋₄ alkyl, andeach Q² is hydrogen or methyl.

In a preferred embodiment, the monohydric phenol comprises2,6-dimethylphenol (hereinafter “DMP”) and 2,3,6-trimethylphenol(hereinafter “TMP”). In this embodiment, the DMP and TMP may be used inany proportion, from weight ratios of 99:1 to 1:99. However, it may bepreferred to use a DMP:TMP weight ratio of about 1:1 to about 20:1.

The oxidative coupling of the monohydric phenol uses anoxygen-containing gas, which is typically oxygen (O₂) or air, withoxygen being preferred.

The monohydric phenol is oxidatively coupled in the presence of asolvent and a complex metal catalyst. Suitable organic solvents includealiphatic alcohols, ketones, aliphatic and aromatic hydrocarbons,chlorohydrocarbons, nitrohydrocarbons, ethers, esters, amides, mixedether-esters, sulfoxides, and the like, and combinations comprising atleast one of the foregoing organic solvents, providing they do notinterfere with or enter into the oxidation reaction. In a preferredembodiment, the solvent comprises a C₆-C₁₈ aromatic hydrocarbon,including, for example, toluene, xylenes, and the like, and mixturesthereof. A highly preferred solvent is toluene.

The solvent may comprise, in addition to a C₆-C₁₈ aromatic hydrocarbon,a C₃-C₈ aliphatic alcohol that is a poor solvent for the poly(aryleneether), such as, for example, n-propanol, isopropanol, n-butanol,t-butanol, n-pentanol, and the like, and combinations comprising atleast one of the foregoing C₃-C₈ aliphatic alcohols. A preferred C₃-C₈aliphatic alcohol is n-butanol. The solvent may further comprise, inaddition to a C₆-C₁₈ aromatic hydrocarbon and a C₃-C₈ aliphatic alcohol,methanol or ethanol, which act as an anti-solvent for the poly(aryleneether). The C₆-C₁₈ aromatic hydrocarbon, the C₃-C₈ aliphatic alcohol,and the methanol or ethanol may be combined in any proportion, but itmay be preferred that the solvent comprise at least about 50 weightpercent of the C₆-C₁₈ aromatic hydrocarbon.

The complex metal catalyst may comprise a metal ion. Preferred metalions include ions from Group VIB, VIIB, or IB of the periodic table, andcombinations thereof. Of these, ions of chromium, manganese, cobalt,copper, and combinations comprising at least one of the foregoing ionsmay be preferred, with copper ions (Cu⁺ and Cu⁺⁺) being highlypreferred.

The complex metal catalyst may further comprise a nitrogen-containingligand. The nitrogen-containing ligand may include, for example,alkylenediamine ligands, primary monoamines, secondary monoamines,tertiary monoamines, aminoalcohols, oxines, combinations comprising atleast one of the foregoing nitrogen-containing ligands, or the like.

Suitable alkylenediamine ligands include those having the formula

(R^(b))₂N—R^(a)—N(R^(b))₂

wherein R^(a) is a substituted or unsubstituted divalent residue whereintwo or three aliphatic carbon atoms form the closest link between thetwo diamine nitrogen atoms; and each R^(b) is independently hydrogen orC₁-C₈ alkyl. Preferred alkylenediamine ligands include those in whichR^(a) is ethylene (—CH₂CH₂—) or trimethylene (—CH₂CH₂CH₂—), and eachR^(b) is independently hydrogen, isopropyl, or a C₄-C₈ alpha-tertiaryalkyl group. Highly preferred alkylenediamine ligands include N,N-di-t-butylethylenediamine and N,N,N′,N′-tetramethyl-1,3-diaminopropane.

Suitable primary monoamines include C₃-C₁₂ primary alkylamines, such as,for example, n-propylamine, i-propylamine, n-butylamine, sec-butylamine,t-butylamine, n-penylamine, n-hexylamine, cyclohexylamine, combinationscomprising at least one of the foregoing primary monoamines, and thelike. A highly preferred primary monoamine is n-butylamine.

Suitable secondary monoamines include secondary monoamines having thestructure (R^(c))(R^(d))NH, wherein R^(c) and R^(d) are eachindependently a C₁-C₁₁ alkyl group, with the proviso that R^(c) andR^(d) collectively have a total of four to twelve carbon atoms. Examplesof secondary monoamines include di-n-propylamine, n-propyl-n-butylamine,di-n-butylamine, d-t-butylamine, n-butyl-n-penylamine, di-n-hexylamine,and the like, with di-n-butylamine being preferred.

Suitable tertiary monoamines include tertiary monoamines having thestructure (R^(e))(R^(f))(R^(g))N, wherein R^(e) and R^(f) and R^(g) areeach independently a C₁-C₁₆ alkyl group, with the proviso that R^(e) andR^(f) and R^(g) collectively have a total of four to eighteen carbonatoms. Examples of tertiary monoamines include triethylamine,tri-n-propylamine, tri-n-butylamine, dimethyl-n-butylamine,dimethyl-n-penylamine, diethyl-n-butylamine, triycyclohexylamine, andthe like. In addition, cyclic tertiary amines, such as pyridine,alpha-collidine, gamma-picoline, and the like, can be used. Highlypreferred tertiary monoamines include dimethyl-n-butylamine. Additionalprimary, secondary, and tertiary amines are described in U.S. Pat. Nos.3,306,874 and 3,306,875 to Hay.

Suitable aminoalcohols include C₄-C₁₂ aminoalcohols having one nitrogenatom and an alcohol oxygen, wherein at least two carbon atoms separatethe amino nitrogen and the alcohol oxygen. Examples of aminoalcoholsinclude N,N-diethylethanolamine, 4-butanolamine,N-methyl-4-butanolamine, diethanolamine, triethanolamine,N-phenyl-ethanolamine, and the like, and combinations comprising atleast one of the foregoing aminoalcohols. Highly preferred aminoalcoholsinclude triethanolamine and N-phenylkethanolamine.

Suitable oxines include those having the formula

wherein R¹-R⁶ are each independently hydrogen, halogen, hydroxyl, nitro,amino, C₁-C₆ alkyl, or C₁-C₆ alkoxyl. Examples of oxines include oxine,5-methyloxine, 5-hydroxyoxine, 5-nitroxine, 5-aminoxine, 2-methyloxine,and the like, and combinations comprising at least one of the foregoingoxines. Highly preferred oxines include oxine and 5-methyloxine.

The alkylenediamine ligands, primary monoamines, secondary monoamines,aminoalcohols, and oxines, when present, may be used at about 0.01 toabout 25 moles per 100 moles of monohydric phenol. The tertiarymonoamines may be used at about 0.1 to about 1,500 moles per 100 molesof monohydric phenol. Selections of appropriate concentrations withinthese ranges may be made by those of ordinary skill in the art withoutundue experimentation, and selected concentrations may reflect thepresence of other reaction components or products, such as water, thatmay affect catalyst efficiency. A suitable molar ratio of complex metalcatalyst (measured as moles of metal) to phenol is about 1:50 to about1:400, with about 1:100 to about 1:200 being preferred.

The complex metal catalyst may, optionally, further include a halide ionsuch as chloride, bromide, or iodide. When employed, halide ions may besupplied to the reaction mixture in the form of an alkali metal salt oran alkaline earth metal salt at a concentration of about 0.1 mole toabout 150 moles per 100 moles of phenolic monomer.

In a preferred embodiment, the complex metal catalyst comprises copperion, a secondary alkylenediamine ligand, a secondary monoamine, and atertiary monoamine. In a highly preferred embodiment, the complex metalcatalyst comprises copper ion, N,N′-di-t-butylethylenediamine,di-n-butylamine, and dimethyl-n-butylamine.

The process and reaction conditions for the polymerization, such asreaction time, temperature, oxygen flow rate, and the like may bemodified based on the target molecular weight and monomer composition.The endpoint of the polymerization may conveniently be determined withan in-line viscosity meter. Other methods such as making molecularweight measurements, running to a predetermined reaction time,controlling to a specified end group concentration, or the oxygenconcentration in solution may also be utilized.

The temperature to carry out the polymerization stage is generally about0° C. to about 95° C. Within this range, it may be preferred to use atemperature of at least about 35° C. Also within this range, it may bepreferred to use a temperature up to 45° C. At temperaturessubstantially higher than about 95° C., side reactions can occur leadingto reaction by-products, and at temperatures substantially lower thanabout 0° C., ice crystals may form in the solution.

The method may, optionally, further comprise recovering the complexmetal catalyst with an aqueous solution. Many diverse extractants orchelating agents may be used to complex with the catalyst after the endof the polymerization reaction. For example, sulfuric acid, acetic acid,ammonium salts, bisulfate salts and various chelating agents may beused. When these materials are added to a poly(arylene ether) reactionsolution, the complex metal catalyst becomes poisoned and furtheroxidation does not take place. Many different materials may be used butit is preferred to employ those chelating agents that are disclosed inU.S. Pat. No. 3,838,102 to Bennett et al. Useful chelating agentsinclude polyfunctional carboxylic acid containing compounds, such as,for example, polyalkylenepolyamine polycarboxylic acids,aminopolycarboxylic acids, aminocarboxylic acids, aminopolycarboxylicacids, aminocarboxylic acids, polycarboxylic acids and their alkalimetal, alkaline earth metal or mixed alkali metal-alkaline earth metalsalts. Specific examples of chelating agents include, for example,sodium potassium tartrate, nitrilotriacetic acid (NTA), citric acid,glycine, ethylenediaminetetraacetic acid (EDTA),hydroxyethylenediaminetriacetic acid, diethylenetriaminepentaaceticacid, salts of the foregoing chelating agents, combinations comprisingat least one of the foregoing chelating agents, and the like. Especiallypreferred chelating agents include ethylenediaminetetraacetic acid or amono-, di-, tri- and tetrasodium salt thereof. The resulting coppercomplex can be referred to as a copper carboxylate complex.

The chelated metallic catalyst component may be extracted with the waterproduced in the polymerization reaction through the use of aliquid/liquid centrifuge. Alternatively, additional water may be addedto the mixture to improve the mixing and extraction efficiency. Ineither case, the chelated metallic catalyst component dissolved in thewater phase may be separated from the poly(arylene ether)/toluenesolution by the use of a liquid/liquid centrifuge. The preferredextraction liquid is an aqueous solution of lower alkanol, for example,a mixture of water and an alkanol having from 1 to about 4 carbon atoms.Generally from about 1% to about 80% by volume of the alkanol may beemployed,based on the total volume of the aqueous solution of loweralkanol. The volume ratio of the aqueous liquid extractant to discreteorganic phase may vary from about 0.01:1 to about 10:1.

The reaction medium may comprise an aqueous environment. Anti-solventscan also be utilized in combination with the aqueous media to help drivethe precipitation of the copper (I) species. The selection of anappropriate anti-solvent is based partially on the solubilitycoefficient of the copper (I) species that is being precipitated. Thehalides are highly insoluble in water, log(K_(sp)) values at 25° C. are−4.49, −8.23, and −11.96 for CuCl, CuBr, and CuI, respectively.Solubility in water is increased by the presence of excess of halideions due to the formation of, e.g., CuCl₂ ⁻, CuCl₃ ²⁻, and CuCl₄ ³⁻, andby other complexing species. Examples of anti-solvents include lowmolecular weight aliphatic and aromatic hydrocarbons, ketones, alcohols,and the like, which in themselves would have some solubility in theaqueous solution. One skilled in the art would be able to select anappropriate type and amount of anti-solvent, if any was utilized.

The method comprises removing a portion of the solvent to produce aconcentrated solution having a cloud point, T_(cloud). (T_(cloud) andits determination are discussed in detail below.) This concentrationstep, sometimes referred to as pre-concentration, may, for example, beconducted after removal of the complex metal catalyst. Thepre-concentration step may preferably produce a concentrated solutionhaving about 20 to about 60 weight percent of the poly(arylene ether).Determining the desired poly(arylene ether) weight percent will dependon the solvent, as well as the monomer composition and intrinsicviscosity of the poly(arylene ether). Within this range, it may bepreferred to have a poly(arylene ether) concentration of at least about25 weight percent, yet more preferably at least about 30 weight percent.Also within the above range, it may be preferred to have a poly(aryleneether) concentration of up to about 55 weight percent, more preferablyup to about 50 weight percent, yet more preferably up to about 45 weightpercent. In a preferred embodiment, the removing a portion of thesolvent to produce a concentrated solution may be conducted at atemperature of at least about (T_(cloud)−10° C.), more preferably atleast about (T_(cloud)−5° C.), yet more preferably at least aboutT_(cloud), even more preferably at least about (T_(cloud)+5° C.), stillmore preferably at least about (T_(cloud)+10° C.).

Any suitable method for pre-concentration may be employed. For example,the pre-concentration may be carried out by preheating the solutionabove its atmospheric boiling point at a pressure modestly elevatedabove one atmosphere (so that no boiling takes place in the heatexchanger) followed by flashing the solution to a lower pressure andtemperature, whereby vaporization of a substantial part of the solventtakes place and the required heat of vaporization is supplied by theheat transferred in the heat exchanger as sensible heat of the solution.

The method further comprises combining the concentrated solution with ananti-solvent to precipitate the poly(arylene ether), wherein theconcentrated solution has a temperature of at least about (T_(cloud)−10°C.) immediately before it is combined with the anti-solvent. Throughextensive experimentation, the present inventors found that whileconventional processes for poly(arylene ether) synthesis and isolationmay lead to unacceptably high levels of fines, reduced levels of finesare obtained when the concentrated solution has a temperature of atleast about (T_(cloud)−10° C.) immediately before it is combined withthe anti-solvent. The cloud point, T_(cloud), is a property of theconcentrated solution resulting from the pre-concentration step. Itcorresponds to the temperature at which turbidity is first observed fora cooling solution of a poly(arylene ether), and it is influenced byfactors including the poly (arylene ether)'s monomer composition andintrinsic viscosity and concentration, as well as the identity of thesolvent. A detailed procedure for determining a cloud point is providedbelow in Examples 2-26. For a given poly(arylene ether) dissolved in agiven solvent, the T_(cloud) value may be determined by preparing thesolution in its homogeneous state and gradually decreasing thetemperature until turbidity is first observed. By measuring T_(cloud)for variations in poly(arylene ether) monomer composition, intrinsicviscosity, and concentration, it is possible to derive an equationrelating T_(cloud) to these variables for any poly(aryleneether)/solvent system.

While it has been found that poly(arylene ether) powders havingacceptably low fines contents may be produced by precipitation when aconcentrated solution having a temperature of at least (T_(cloud)−10°C.) is combined with an anti-solvent, it may be preferable to furtherreduce fines content by using a concentrate temperature of at leastabout (T_(cloud)−5° C.), more preferably at least about (T_(cloud)), yetmore preferably at least about (T_(cloud)+5° C.), and even morepreferably at least about (T_(cloud)+10° C.).

By specifying the temperature of the concentrated solution “immediatelybefore” it is combined with the anti-solvent, it is meant that theconcentrated solution has the specified temperature as it is combinedwith the anti-solvent. As a practical matter, the temperature of theconcentrated solution may be determined at any time within about 30seconds of mixing with the anti-solvent. Another way of expressing thetemperature limitation is to say that the process comprises removing aportion of the solvent to produce a concentrated solution having a cloudpoint, T_(cloud); adjusting the temperature of the concentrated solutionto at least about (T_(cloud)−10° C.); and combining the concentratedsolution with an anti-solvent to precipitate the poly (arylene ether).

In one embodiment, the concentrated solution has a temperature greaterthan T_(cloud) and is homogeneous immediately before it is mixed withthe anti-solvent. Homogeneity of the solution corresponds to the absenceof any turbidity in the solution and may be determined using the samevisual observation techniques employed for T_(cloud) determination. In ahighly preferred embodiment, a temperature of at least about(T_(cloud)+5° C.) is maintained in the poly(arylene ether)-containingsolution from the beginning of the concentration step to the momentimmediately before the resulting concentrated solution is combined withanti-solvent.

In one embodiment, T_(cloud) is at least about 60° C., preferably atleast about 70° C., more preferably at least about 80° C., yet morepreferably at least about 90° C. It should be noted that solutions ofthe homopolymer poly(2,6-dimethyl-1,4-phenylene ether) in aromaticsolvents such as toluene typically do not exhibit a cloud point. Rather,as such solutions of poly(2,6-dimethyl-1,4-phenylene ether) areconcentrated, they may form a gelatinous phase without the discretesolid particles characteristic of a cloud point.

Suitable anti-solvents include lower alkanols having one to about tencarbon atoms, such as methanol, and the like; ketones having three toabout ten carbon atoms, such as acetone, and the like; and alkaneshaving five to about ten carbon atoms, such as hexane; and the like; andcombinations comprising at least one of the foregoing anti-solvents. Apreferred anti-solvent comprises methanol. A highly preferredanti-solvent comprises about 70 to 100 weight percent methanol, 0 toabout 20 weight percent toluene, and 0 to about 10 weight percent water.The anti-solvent may be employed at a range of amounts relative to theamount of the organic solvent, with the optimum amount depending on theidentities of the organic solvent and anti-solvent, as well as theconcentration, intrinsic viscosity, and monomer composition of thepoly(arylene ether) product. For example, when the poly(arylene ether)is a random copolymer having an intrinsic viscosity of 0.36 dL/g and acomposition of 82 weight percent 2,6-dimethyl-1,4-phenylene ether unitsand 18 weight percent 2,3,6-dimethyl-1,4-phenylene ether units, theorganic solvent is toluene, and the anti-solvent is methanol, atoluene:methanol weight ratio of about 1:1.5 to about 1:5 may besuitable.

While there is no particular limitation on the temperature of theanti-solvent solution before it is combined with the concentratedsolution, it may be preferred to select an anti-solvent temperature sothat combining the concentrated solution with the anti-solvent producesa mixture having a temperature of about 20° C. to about 50° C. Withinthis range, it may be preferable to use a mixture temperature of atleast about 25° C., more preferably at least about 35° C. Also withinthis range, it may be preferable to use a mixture temperature up toabout 45° C.

There is no particular limitation on the apparatus used to perform theprecipitation. The precipitation may be conducted, for example, in astirred tank vessel or a high-shear impeller. Suitable high shearimpellers are commercially available from, for example, Wilhelm SieferGmbH & Co., Velbert, Germany. The shear rates during precipitation inthe stirred tank and in the high shear homogenizer may be about 500sec⁻¹ to 50,000 sec⁻¹.

The method may, optionally, further comprise isolation of theprecipitated poly (arylene ether) using any conventional filtration orsolid/liquid separation technique. Suitable filtration apparatusesinclude rotating filters, continuous rotary vacuum filters, continuousmoving bed filters, batch filters, and the like. Suitable solid/liquidseparation apparatuses include continuous solid/liquid centrifuges.

The method may, optionally, further comprise washing of the filteredpoly(arylene ether). Washing may be performed, for example, withadditional anti-solvent directly on the filter or by mixing the “powderwetcake” from the filter or solid/liquid separation apparatus withadditional anti-solvent in a stirred tank. A preferred method of washingthe filtered poly(arylene ether) uses a two-stage reslurry andsolid/liquid separation process scheme. In this embodiment, the wetcakefrom the filter may be washed with anti-solvent in a stirred tank; thepoly(arylene ether)/solvent/anti-solvent mixture may then be separatedin a solid/liquid continuous centrifuge and the poly(arylene ether)wetcake from the centrifuge may be mixed a second time with anti-solventin a continuous stirred tank, followed by a second solid/liquidseparation in a second solid/liquid centrifuge.

It may be preferred that the precipitated poly(arylene ether) comprisesup to about 20 weight percent, more preferably up to about 15 weightpercent, of particles smaller than 38 micrometers.

There is no particular limitation on the intrinsic viscosity of thepoly(arylene ether) formed by the method. For some applications, it maybe preferred to use a poly (arylene ether) having an intrinsic viscosityof at least about 0.20 dL/g, more preferably at least about 0.25 dL/g,yet more preferably at least about 0.30 dL/g, as measured in chloroformat 25° C.

In one embodiment, the method of preparing a poly(arylene ether),comprises: oxidatively coupling 2,6-dimethylphenol and2,3,6-trimethylphenol using an oxygen-containing gas in the presence oftoluene and a complex copper catalyst to produce a poly(arylene ether)copolymer resin; removing a portion of the solvent to produce aconcentrated solution having a cloud point, T_(cloud); and combining theconcentrated solution with an anti-solvent to precipitate thepoly(arylene ether); wherein the concentrated solution has atemperature, T, immediately before it is combined with the anti-solvent;and wherein T satisfies the inequality$T > \left( {\frac{\varphi_{s} - \left( {{0.296 \times {IV}} + {1.27 \times {TMP}} - 35.7} \right)}{1.97\left( {1 - {0.00795 \times {IV}} - {0.0249 \times {TMP}}} \right)} - 10} \right)$

where ø_(S) is the polymer concentration (expressed in weight percent),IV is the intrinsic viscosity of the copolymer in chloroform at 25° C.(expressed in mL/g), and TMP is the 2,3,6-trimethylphenol content of thecopolymer (expressed in weight %).

In another embodiment, the method of preparing a poly(arylene ether),comprises: oxidatively coupling 2,6-dimethylphenol and2,3,6-trimethylphenol using an oxygen-containing gas in the presence oftoluene and a complex copper catalyst to produce a poly(arylene ether)copolymer resin; wherein the weight ratio of 2,6-dimethylphenol to2,3,6-trimethylphenol is about 3:1 to about 6:1; recovering the complexmetal catalyst with an aqueous solution; removing a portion of thesolvent to produce a concentrated solution comprising about 30 to about45 weight percent of the poly (arylene ether) copolymer resin and havinga cloud point, T_(cloud); and combining the concentrated solution withan anti-solvent to precipitate the poly(arylene ether); wherein theconcentrated solution has a temperature of at least about (T_(cloud)+5°C.) immediately before it is combined with the anti-solvent; wherein theprecipitated poly (arylene ether) has an intrinsic viscosity of about0.25 to about 0.50 dL/g; and wherein the precipitated poly(aryleneether) comprises up to about 15 weight percent of particles smaller than38 micrometers.

In another embodiment, the method of preparing a poly(arylene ether),comprises: oxidatively coupling 2,6-dimethylphenol and2,3,6-trimethylphenol using an oxygen-containing gas in the presence oftoluene and a complex copper catalyst to produce a poly(arylene ether)copolymer resin; wherein the weight ratio of 2,6-dimethylphenol to2,3,6-trimethylphenol is about 3:1 to about 6:1; recovering the complexmetal catalyst with an aqueous solution; removing a portion of thesolvent to produce a solution having about 30 to about 45 weight percentpoly(arylene ether); and combining the concentrated solution with ananti-solvent to precipitate the poly (arylene ether); wherein theconcentrated solution has a temperature of at least about 80° C.immediately before it is combined with the anti-solvent; wherein theprecipitated poly(arylene ether) has an intrinsic viscosity of about0.25 to about 0.40 dL/g; and wherein the precipitated poly(aryleneether) comprises up to about 15 weight percent of particles smaller than38 micrometers.

Another embodiment is a poly(arylene ether) prepared by any of theabove-described methods, especially a poly(arylene ether) comprising upto about 20 weight percent, preferably up to about 15 weight percent, ofparticles smaller than 38 micrometers.

The invention is further illustrated by the following non-limitingexamples.

EXAMPLE 1

This example illustrates the synthesis and isolation of a poly(aryleneether) copolymer having 18 weight percent of repeating units derivedfrom 2,3,6-trimethylphenol and 82 weight percent of units derived from2,6-dimethylphenol. In a reactor were combined cuprous oxide (Cu₂O;0.027 kg, obtained from American Chemet as purple copper) dissolved inhydrobromic acid (0.423 kg as 48% aqueous solution, CAS Reg.No.10035-10-6, obtained from Great Lakes),N,N′-di-t-butylethylenediamine (0.119 kg, DBEDA, CAS Reg. No. 4062-60-6obtained from Celanese), di-n-butylamine (1.616 kg, DBA, CAS Reg. No.111-92-2, obtained from Celanese), N,N-dimethylbutylamine (2.675 kg,DMBA, CAS Reg. No. 927-62-8, obtained from Celanese), atetraalkylammonium chloride surfactant (0.059 kg, CAS Reg. No.5137-55-3, obtained from Cognis as Aliquat), 2,6-dimethylphenol (5.361kg) and toluene solvent (140.06 kg). Over the course of thepolymerization reaction, additional 2,6-dimethylphenol (30.377 kg) wasadded, along with 2,3,6-trimethylphenol (7.845 kg). During thepolymerization, the nitrogen flow rate was 61.3 liters/minute, theoxygen flow rate was 46.2 liters/minute, and the temperature increasedgradually from 29.4° C. to 55.0° C. After the completion of thepolymerization reaction, the copper catalyst was separated from thepolymer by mixing the reactor effluent with an aqueous solution ofnitrilotriacetic acid (0.871 kg as a 60% solution in water, CAS Reg. No.139-13-9, obtained from Solutia). The two phase solution was separatedusing a liquid-liquid centrifuge. The polymer phase was concentrated to38 weight percent polymer by flashing toluene at atmospheric pressure.The product copolymer was precipitated from the concentrated polymersolution by combining the solution (at 88° C.) in a stirred tank vesselwith methanol (at 15° C.) at 1:2 weight/weight ratio of polymersolution:methanol. The resulting slurry was passed through a rotaryvacuum filter and the wetcake was re-slurried with methanol. This slurrywas centrifuged and the separated solid particles were dried in a rotarypaddle dryer.

EXAMPLES 2-26

These examples illustrate the determination of cloud points for toluenesolutions of poly(2,6-dimethyl-1,4-phenyleneether-co-2,3,6-trimethyl-1,4-phenylene ether) as a function of copolymerconcentration, copolymer intrinsic viscosity, and copolymer composition.Copolymers having intrinsic viscosities of 35.3 mL/g to 41.6 mL/g, and15, 18, and 21 weight percent of units derived from2,3,6-trimethylphenol (TMP) were synthesized according to the procedureof Example 1. For a given copolymer solubility determination, anisolated poly(arylene ether) copolymer was dissolved at 10 to 30 weightpercent in toluene at 90° C. The temperature of the solution wasdecreased at a rate of about 1° C. per minute and the temperature atwhich the first turbidity was observed was recorded as the cloud point,T_(cloud). Results are presented in Table 1.

TABLE 1 copolymer copolymer Ex. TMP content concentration observedT_(cloud) No. (wt %) I.V. (mL/g) (wt %) (° C.) 2 15 35.3 10 21.5 3 1535.3 15 33.0 4 15 35.3 20 38.5 5 15 35.3 25 47.0 6 15 35.3 30 55.0 7 1835.3 10 30.5 8 18 35.3 15 36.0 9 18 35.3 20 41.5 10 18 35.3 25 46.0 1118 35.3 30 54.0 12 18 41.0 10 32.0 13 18 41.0 15 38.0 14 18 41.0 20 43.515 18 41.0 25 50.0 16 18 41.0 30 62.5 17 21 35.8 10 35.0 18 21 35.8 1539.5 19 21 35.8 20 46.0 20 21 35.8 25 52.0 21 21 35.8 30 82.0 22 21 41.610 35.5 23 21 41.6 15 41.5 24 21 41.6 20 49.0 25 21 41.6 25 95.0 26 2141.6 30 99.0

Using linear regression techniques, the data were used to generate theequation (I)

ø_(S)=(0.30±0.15)IV+(1.27±0.31)TMP−(35.7±6.1)+(1.97±0.41)T_(cloud)(1−(0.0080±0.0013)IV (0.0249±0.0026)*TMP)  (I)

where ø_(S) is the copolymer solubility (expressed in weight percent),IV is the copolymer intrinsic viscosity in chloroform at 25° C.(expressed in mL/g), TMP is weight percent of units derived from TMP inthe copolymer (expressed in weight percent), and T_(cloud) is the cloudpoint (expressed in ° C.). Uncertainties expressed for each coefficientand the intercept represent 95% confidence intervals. Equation (I) canbe solved for T_(cloud) to generate equation (II):

T_(cloud)=[ø_(S)−(0.2961IV+1.27TMP−35.7)]/[1.97(1−0.00795IV−0.0249TMP)]  (II)

These examples demonstrate the use of controlled variations in copolymerTMP content, intrinsic viscosity, and solution concentration to generatean equation to predict cloud point as a function of these variables.Although this example uses toluene as the solvent, the method may beapplied to solutions in other solvents.

EXAMPLES 27-34

These examples demonstrate the effect of pre-concentration temperatureon the generation of fines (i.e., particles smaller than 38 micrometers)in a precipitated poly (arylene ether) copolymer. The method of Example1 was used to prepare a poly (arylene ether) random copolymer having anintrinsic viscosity of 36.4 mL/g, and 18 weight percent of repeatingunits derived from TMP. A sample of the isolated powder copolymer wasdissolved in toluene to generate a 36 weight percent solution. Theprecipitation was conducted batch-wise in a stirred vessel provided witha high shear mixer, operated at high rotating speed (7,500 rpm or 15,000rpm) to achieve high shear mixing; at the start of the experiment, theanti-solvent was present in the vessel. The anti-solvent contained 94.9weight percent methanol, 3.1 weight percent toluene, and 2.0 weightpercent water. Then the poly(arylene ether) solution in toluene—atdifferent solids concentrations as indicated in the table below—wasadded within 30 seconds to the vessel in a 1:2.5 weight/weight ratio ofpoly(arylene ether)/toluene solution to anti-solvent. Temperature andprecipitation conditions were varied for 8 samples as detailed in Table2. The temperature of the poly(arylene ether)/toluene solution that wasadded to the methanol anti-solvent was either 65° C. or 85° C. Note thata 36 weight percent solution of this copolymer in toluene has a cloudpoint of 75° C. The temperature of the methanol was selected so thatmixing of the poly(arylene ether)/toluene solution and the methanolwould yield a mixture having a temperature of 40° C. This 40° C.temperature was maintained during the precipitation. The precipitatedcopolymer was filtered over a Schliecher and Schull “Black Ribbon”filter paper on a Buchner filter, applying vacuum; after filtration, theremaining filtercake was washed with 1,200 grams of methanol.Subsequently the washed filtercake was dried in a vacuum oven at 125° C.for about 4 hours.

For each example, the particle size distribution of the precipitatedcopolymer was determined using a PSD Analyzer obtained from MalvernInstruments Ltd., which employs a laser diffraction technique to sortparticles into six size categories: less than 38 micrometers, 38-63micrometers, 63-125 micrometers, 125-425 micrometers, 425-710micrometers, and greater than 710 micrometers. The results, presented inTable 2 and FIG. 1, show that use of a preconcentration temperature of85° C. led to the generation of fewer fines than a preconcentrationtemperature of 65° C.

TABLE 2 pre- precip. conc. shear temp. rate particle size distribution(wt %) Ex. No. (° C.) (rpm) <38 μm 38-63 μm 63-125 μm 125-425 μm 425-710μm >710 μm 27 85  7,500 14.7 8.5 20.4 46.3 9.5 0.6 28 85  7,500 14.7 7.918.0 43.9 10.1  5.3 29 85  7,500 11.1 7.3 17.9 45.1 11.9  6.7 30 8515,000 13.6 9.4 22.1 47.4 6.5 1.1 31 85 15,000 12.7 8.8 20.6 51.3 6.60.1 32 85 15,000 13.0 8.9 20.4 46.7 8.6 2.4 33 65  7,500 23.7 11.6  22.726.2 6.1 9.8 34 65 15,000 21.2 13.9  28.4 34.2 1.7 0.6

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing fromessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. A method of preparing a poly(arylene ether),comprising: oxidatively coupling a monohydric phenol using anoxygen-containing gas in the presence of a solvent and a complex metalcatalyst to produce a poly (arylene ether) resin; removing a portion ofthe solvent to produce a concentrated solution having a cloud point,T_(cloud); adjusting the temperature of the concentrated solution to atleast about (T_(cloud)−10° C.); and combining the concentrated solutionwith an anti-solvent to precipitate the poly (arylene ether).
 2. Themethod of claim 1, wherein the monohydric phenol comprises a monohydricphenol having the formula:

wherein each Q¹ is independently selected from the group consisting ofhalogen, C₁-C₇ primary or secondary alkyl, phenyl, C₁-C₇ haloalkyl,C₁-C₇ aminoalkyl, C₁-C₇ hydrocarbonoxy, and C₂-C₇ halohydrocarbonoxywherein at least two carbon atoms separate the halogen and oxygen atoms;and each Q² is independently selected from the group consisting ofhydrogen, halogen, C₁-C₇ primary or secondary alkyl, phenyl, C₁-C₇haloalkyl, C₁-C₇ hydrocarbonoxy, and C₂-C₇ halohydrocarbonoxy wherein atleast two carbon atoms separate the halogen and oxygen atoms.
 3. Themethod of claim 1, wherein the monohydric phenol comprises2,6-dimethylphenol and 2,3,6-trimethylphenol.
 4. The method of claim 1,wherein the monohydric phenol comprises 2,6-dimethylphenol and2,3,6-trimethylphenol in a weight ratio of about 1:1 to about 20:1. 5.The method of claim 1, wherein the solvent comprises a C₆-C₁₈ aromatichydrocarbon.
 6. The method of claim 5, wherein the solvent furthercomprises a C₃-C₈ aliphatic alcohol.
 7. The method of claim 6, whereinthe solvent further comprises methanol, ethanol, or a mixture comprisingat least one of the foregoing solvents.
 8. The method of claim 1,wherein the complex metal catalyst comprises a metal ion from Group VIB,Group VIIB, or Group IB of the periodic table.
 9. The method of claim 1,wherein the complex metal catalyst comprises chromium, manganese,cobalt, copper, or a combination comprising at least one of theforegoing metals.
 10. The method of claim 1, wherein the complex metalcatalyst comprises an alkylenediamine ligand having the formula(R^(b))₂N—R^(a)—N(R^(b))₂ wherein R^(a) is a substituted orunsubstituted divalent residue wherein two or three aliphatic carbonatoms form the closest link between the two diamine nitrogen atoms; andeach R^(b) is independently hydrogen or C₁-C₈ alkyl.
 11. The method ofclaim 10, wherein each R^(a) is ethylene or trimethylene, and each R^(b)is independently hydrogen, isopropyl, or a C₄-C₈ alpha-tertiary alkylgroup.
 12. The method of claim 10, wherein the alkylenediamine ligand isN,N,N′,N′-tetramethyl-1,3-diaminopropane.
 13. The method of claim 10,wherein the alkylenediamine ligand is N,N′-di-t-butylethylenediamine.14. The method of claim 1, wherein the complex metal catalyst comprisesa C₄-C₁₂ secondary monoamine.
 15. The method of claim 14, wherein thesecondary monoamine comprises di-n-butylamine.
 16. The method of claim1, wherein the complex metal catalyst comprises a C₄-C₁₂ aminoalcohol,wherein at least two carbon atoms separate the amino nitrogen and thealcohol oxygen.
 17. The method of claim 16, wherein the aminoalcohol istriethanolamine or N-phenyl-ethanolamine.
 18. The method of claim 1,wherein the complex metal catalyst comprises an oxine having the formula

wherein R¹-R⁶ are each independently selected from the group consistingof hydrogen, halogen, hydroxyl, nitro, amino, C₁-C₆ alkyl, and C₁-C₆alkoxyl.
 19. The method of claim 1, wherein the complex metal catalystcomprises a tertiary monoamine having the structure(R^(e))(R^(f))(R^(g))N, wherein R^(e) and R^(f) and R^(g) are eachindependently a C₁-C₁₆ alkyl group, with the proviso that R^(e) andR^(f) and R^(g) collectively have a total of four to eighteen carbonatoms.
 20. The method of claim 19, wherein the tertiary monoaminecomprises dimethyl-n-butylamine.
 21. The method of claim 1, wherein thecomplex metal catalyst comprises a C₃-C₁₂ primary alkylamine.
 22. Themethod of claim 21, wherein the primary alkylamine is n-butylamine. 23.The method of claim 1, wherein the concentrated solution comprises about20 to about 60 weight percent of the poly(arylene ether).
 24. The methodof claim 1, wherein the temperature of the concentrated solution isadjusted to at least about (T_(cloud)−5° C.).
 25. The method of claim 1,wherein the temperature of the concentrated solution is adjusted to atleast about T_(cloud).
 26. The method of claim 1, wherein thetemperature of the concentrated solution is adjusted to at least about(T_(cloud)+5° C.).
 27. The method of claim 1, wherein the anti-solventcomprises an anti-solvent selected from the group consisting of alkanolshaving one to about ten carbon atoms, ketones having three to about tencarbon atoms, alkanes having five to about ten carbon atoms, andcombinations comprising at least one of the foregoing anti-solvents. 28.The method of claim 1, wherein the anti-solvent comprises methanol. 29.The method of claim 1, wherein the anti-solvent comprises about 70 to100 weight percent methanol, 0 to about 20 weight percent toluene, and 0to about 10 weight percent water.
 30. The method of claim 1, whereinT_(cloud) is at least about 60° C.
 31. The method of claim 1, whereinthe removing a portion of the solvent is conducted at a temperature ofat least about T_(cloud)−10° C).
 32. The method of claim 1, whereinremoving a portion of the solvent is conducted at a temperature of atleast about T_(cloud).
 33. The method of claim 1, wherein removing aportion of the solvent is conducted at a temperature of at least about(T_(cloud)+10° C.).
 34. The method of claim 1, wherein the combining theconcentrated solution with an anti-solvent is conducted using a stirredtank vessel or a high-shear impeller.
 35. The method of claim 1, whereinthe combining the concentrated solution with an anti-solvent produces amixture having a temperature of about 20° C. to about 50° C.
 36. Themethod of claim 1, wherein the precipitated poly(arylene ether)comprises up to about 20 weight percent of particles smaller than 38micrometers.
 37. The method of claim 1, wherein the precipitatedpoly(arylene ether) has an intrinsic viscosity of at least about 0.20dL/g as measured in chloroform at 25° C.
 38. The method of claim 1,further comprising recovering the complex metal catalyst with an aqueoussolution.
 39. A method of preparing a poly(arylene ether), comprising:oxidatively coupling a monohydric phenol using an oxygen-containing gasin the presence of a solvent and a complex metal catalyst to produce apoly (arylene ether) resin; removing a portion of the solvent to producea concentrated solution having a cloud point, T_(cloud); and combiningthe concentrated solution with an anti-solvent to precipitate the poly(arylene ether); wherein a temperature of at least about (T_(cloud)−10°C.) is maintained in the poly(arylene ether)-containing solution fromthe beginning of the concentration step to the moment immediately beforethe concentrated solution is combined with anti-solvent.
 40. A method ofpreparing a poly(arylene ether), comprising: oxidatively coupling2,6-dimethylphenol and 2,3,6-trimethylphenol using an oxygen-containinggas in the presence of toluene and a complex copper catalyst to producea poly(arylene ether) copolymer resin; removing a portion of the solventto produce a concentrated solution having a cloud point, T_(cloud); andadjusting the temperature of the concentrated solution to a temperature,T, satisfying the inequality$T > \left( {\frac{\varphi_{s} - \left( {{0.296 \times {IV}} + {1.27 \times {TMP}} - 35.7} \right)}{1.97\left( {1 - {0.00795 \times {IV}} - {0.0249 \times {TMP}}} \right)} - 10} \right)$

 where ø_(S) is the polymer concentration (expressed in weight percent),IV is the intrinsic viscosity of the copolymer in chloroform at 25° C.(expressed in mL/g), and TMP is the 2,3,6-trimethylphenol content of thecopolymer (expressed in weight %); and combining the concentratedsolution with an anti-solvent to precipitate the poly (arylene ether).41. A method of preparing a poly(arylene ether), comprising: oxidativelycoupling 2,6-dimethylphenol and 2,3,6-trimethylphenol using anoxygen-containing gas in the presence of toluene and a complex coppercatalyst to produce a poly(arylene ether) copolymer resin; wherein theweight ratio of 2,6-dimethylphenol to 2,3,6-trimethylphenol is about 3:1to about 6:1; recovering the complex metal catalyst with an aqueoussolution; removing a portion of the solvent to produce a concentratedsolution comprising about 30 to about 45 weight percent of thepoly(arylene ether) copolymer resin and having a cloud point, T_(cloud);adjusting the temperature of the concentrated solution to at least about(T_(cloud)+10° C.); and combining the concentrated solution with ananti-solvent to precipitate the poly (arylene ether); wherein theprecipitated poly(arylene ether) has an intrinsic viscosity of about0.25 to about 0.50 dL/g; and wherein the precipitated poly(aryleneether) comprises up to about 15 weight percent of particles smaller than38 micrometers.
 42. A method of preparing a poly(arylene ether),comprising: oxidatively coupling 2,6-dimethylphenol and2,3,6-trimethylphenol using an oxygen-containing gas in the presence oftoluene and a complex copper catalyst to produce a poly(arylene ether)copolymer resin; wherein the weight ratio of 2,6-dimethylphenol to2,3,6-trimethylphenol is about 3:1 to about 6:1; recovering the complexmetal catalyst with an aqueous solution; removing a portion of thesolvent to produce a solution having about 30 to about 45 weight percentpoly(arylene ether); adjusting the temperature of the concentratedsolution to at least about 80° C.; and combining the concentratedsolution with an anti-solvent to precipitate the poly (arylene ether);wherein the precipitated poly(arylene ether) has an intrinsic viscosityof about 0.25 to about 0.40 dL/g; and wherein the precipitatedpoly(arylene ether) comprises up to about 15 weight percent of particlessmaller than 38 micrometers.
 43. A poly(arylene ether) prepared by themethod of claim 1 and comprising up to about 20 weight percent ofparticles smaller than 38 micrometers.